This invention relates to a method and apparatus for treating a waste stream from a painting operation and, more particularly, to a method and apparatus for processing waste paint sludge, to dry it, remove volatile organic compounds, substantially reduce its weight and volume and to produce a recyclable product.
Treatment of waste in industrial facilities causes a variety of environmental and economic problems. Over the years, increasingly stringent governmental pollution regulations as well as the increased cost of waste disposal have led to escalating concern in the treatment and disposal of waste. The difficulty in disposing of waste materials is exacerbated when the waste includes both organic substances, in the form of hydrocarbons, and inorganic substances. In these circumstances it is desirable to remove the hydrocarbons or at least the volatile organic compounds ("VOC") from the waste before disposal, yet the processing of the hydrocarbon constituents can be troublesome and expensive when the hydrocarbons are still mixed with other inorganic constituents. Furthermore, recently enacted laws regulating the disposal of waste have substantially reduced the amount of hazardous or toxic waste which may be generated and disposed of by individual industrial facilities.
Particularly difficult problems in the treatment of waste are found in the design of paint spraybooth facilities where a large volume of paint overspray and resultant paint sludge waste is generated. Paint sludge includes both organic and inorganic constituents and also substances which are intended to coalesce into a film; these coalescing substances typically make paint sludge very sticky and difficult to handle. Thus, as paint sludge is dewatered and otherwise concentrated, for example by drying, it becomes increasingly more difficult to transport through the heating and conveyance equipment. As a result, no economical and effective method or apparatus has been available for treatment of paint waste sludge. Instead, it has been disposed of by deposit in hazardous waste sites This is an undesirable solution because of cost and potential environmental pollution.
In addition, paint spraybooth facilities generate a very substantial volume of VOC. A typical automotive paint facility may emit as much as 1500 tons of VOC per year at an estimated cost of between $2000 to $5000 per ton. Moreover, VOC emissions from such facilities are subject to stringent environmental control. As a result, a great variety of equipment and methods have been developed to reduce VOC emissions from paint spray-booth facilities. These prior art systems, however, are generally expensive and troublesome to operate. In fact, most such paint facilities are barely able to maintain legal operation because applicable laws are stringent as compared to available technology. No prior art system has been developed which reduces VOC emissions through treatment of the waste paint sludge.
It is therefore desireable to provide a method and apparatus which effectively and economically treat the waste stream or sludge from a paint operation. It is also desirable to provide a method and apparatus which reduce VOC emissions and minimize the weight and volume of waste paint sludge while substantially eliminating its hazardous characteristics.
It has also proven very difficult, if not impossible, to economically and effectively generate a recyclable material from paint sludge. Prior art paint sludge treating systems have not removed all residual water and include substantial amounts of uncured paint resin. These materials may vary in chemistry and amount depending upon the particular painting facility or specific paint formulation being used. Because these materials may also react with other components in new paint or coating products, they are viewed as reactive contaminants. Thus, the discharged product from prior art paint waste treatment systems have not been considered useful as a recyclable material.